Winchester, who has become a touchstone on the disaster circuit thanks to his book on the 1883 eruption of Krakatoa, expected a frisson of alarm. There was none. He did, however, get a question from a middle-aged woman. "When you say extinct," he recalls her asking incredulously. "Do you mean, even Americans?"
This kind of national hubris explains in part why the world's sole superpower remains oddly unprepared for natural disasters. Hurricane Katrina, for example, was widely anticipated and the flooding which ensued was preventable. Indeed, in the year 2001 the Federal Emergency Management Agency (FEMA) named the three most likely scenarios to hit the US. They were a terrorist attack, a levee-breaching hurricane in New Orleans, and an earthquake in San Francisco.
Now that disasters numer one and two have hit, one might think there would be a commotion over the third. Unfortunately, Winchester hasn't seen any springing into action. "I've been out to California," he says, wincing. "It's not a problem of technology, but one of preparedness. They have the equipment: it's just, who is going to staff these things?"
When the Big One occurs, San Francisco will not be able to claim surprise. After all, as Winchester reminds us A Crack in the Edge of the World (Viking, £16.99), the city already had its trial run. At 5:12am on 18 April 1906 an earthquake of an estimated magnitude 7.8 struck the city. The San Andreas Fault, a right-lateral strike-slip fault which runs 800 miles down the California coast, had ruptured in Northern California, sending shockwaves as far north as Oregon and as far south as Los Angeles.
The earthquake was indeed the Katrina of its day. It demolished San Francisco's city hall, made pavements ripple, and displaced more than 200,000 residents. Between several hundred and several thousand people were killed.
"Cement was a relatively new material at that time," says Winchester, "so the structures made with this stood, while anything else just crumbled." As with the hurricane, the death toll had more to do with after-effects rather than the thing itself. Most of the deaths occurred not as a result of falling debris but of the fires which broke out after gas-main breaks.
"The comparisons to Katrina are numerous and just eerie," says Winchester, somewhat wary of his prognostication role. "But the differences are even more striking," he continues, referring to the federal and local government's swift response to the California disaster. By 7:45am, just two and a half hours after the quake, a colourful brigadier-general, Frederick Funston, had gathered an army to report to the city's mayor. Leaflets were printed that looters would be shot, and dramatic rescues began.
At the same time, President Teddy Roosevelt, whom President Bush has often cited as a role model, kick-started a rescue effort that involved the nation's longest hospital train. William Howard Taft, then secretary of war, dispatched some 200,000 rations from the Canadian border. Before long, every tent owned by the US army was in San Francisco.
Although these comparisons are not likely to shine well on the Bush administration, what is most controversial now about A Crack in the Edge of the World is what Winchester has left out of the story. "The San Francisco earthquake was not caused by God," he says unequivocally, "but forces we understand - and understand now better thanks to it."
He buries his account of that fateful day some 250 pages into the book, choosing to explain how the quake occurred, why it happened and, most appropriately, warn people of its coming inevitability. In other words, this is a geology book - not a social history. "If by writing a book like this I could increase awareness of geology and the reasons behind earthquakes and help preparedness," Winchester says, "I'd be very happy."
It is a testament to the climate of rising fundamentalism in America that such a book might be seen as "political". For nowhere does Winchester make room for so-called "intelligent design" or a creative hand. "I am an unapologetic believer in evolution and Darwinian theory," he says. "The notion that 100 million Americans think that the earth is less than 10,000 years old and was created in seven days by an all-powerful being is sort of mind-boggling."
In the wake of Katrina, the director of Repent America, Michael Marcavage, said that "this act of God destroyed a wicked city". The same convulsion of religious fervour and finger-pointing happened after San Francisco, too. Around the world the view was largely that this was the act of a cruel, almighty creator.
Winchester will most likely be called upon to defend the scientific reasons behind this quake when he appears on talk shows to discuss his book. " If I can get across two points: that God did not cause the San Francisco earthquake, and that we need to prepare for a new one," he says, " I'll be happy."
He did not expect ever to have such a large platform to influence thought. For many readers, the beginning of recorded time for him began seven years ago, when his book The Surgeon of Crowthorne - about the eccentric origins of the Oxford English Dictionary - became an unlikely bestseller. But he had by then spent three decades as a journalist. He joined The Guardian in 1970, and spent nine years as a foreign correspondent, in Northern Ireland, Washington DC, and India. It was in the final destination that he had his epiphany about the importance of geology.
"If you drive north from Bombay," he recalls, "suddenly the road tips upward, and in that movement, from when you are sitting in the car to be pressed against the back seat, you realise you have crossed from India into Eurasia - and that is very disturbing." Landscape, since then, has been central to many of his books, from American Heartbeat to Korea: a Walk through the Land of Miracles. A result of these books is his unfailing belief in the moral imperative of conservation, and the need to look for alternative sources of energy. "This planet is all we have," he says.
Most of the new book was written at a farm Winchester owns in the Berkshires of Western Massachusetts. When not in New York or London, he spends as much time as possible there with his partner, the 31-year-old Elaine Ng, who is editor-in-chief of Art Asia Pacific - a magazine which Winchester recently purchased, and which he and Ng publish out of the basement of his New York apartment.
From the wild reaches of Massachusetts, the dangers of natural catastrophe can seem very far away - especially when he is driving one of his two tractors, or arranging the delivery of some geese. But Winchester is away from his rural retreat often enough to know he needs to keep working; that a voice of reason in the care and upkeep of the planet cannot go silent. Just two years ago in Salt Lake City, he was at a conference of the American Association of Petroleum Geologists to receive an award for services to journalism.
He was preparing to give a speech about William Smith, the man credited with creating the first scientific map of England and Wales, subject of Winchester's The Map that Changed the World, and a "sort of hero among geologists". "So there I was, with a speech to give, and just before I get up, the president of the association stands up and says, 'I want to say to you, we've heard all this stuff about conservation and renewal energy'." Winchester pauses and grows deadly serious. For his host went on: "The only proven source of energy is oil. So I have this to say to you, gentlemen: drill, drill, drill".
Simon Winchester, 61, studied geography at Oxford and became a forieign correspondent, working over the course of three decades in Ireland, the US, Asia and Africa. His travels as a reporter inspired books such as Korea: a walk through the land of miracles (1988), The Pacific (1990) and The River at the Centre of the World, about the Yangtse (1996). Published in 1998, The Surgeon of Crowthorne - about the contribution of a Broadmoor inmate to the Oxford English Dictionary - became a surprise international bestseller. It was followed by The Map that Changed the World (2001), Krakatoa (2003) and The Meaning of Everything (2004), also dealing with the OED. His new book, A Crack in the Edge of the World: the great American earthquake of 1906, is published by Viking. Simon Winchester lives in New York and the Berkshire Hills of Massachusetts.